The removal of halogenated organic compounds, such as halogenated aromatic compounds (e.g., chlorobenzenes and chlorophenols) and halogenated aliphatic compounds (e.g., methylene chloride, trichloroethanes and trichloroethylene) from aqueous sources poses serious environmental problems. Typically, such halogenated compounds have been disposed of by separating (e.g., by carbon adsorption or steam stripping with a microporous hollow-fiber membrane) the contaminants from their aqueous environment and then incinerating the contaminants. The incineration of halogenated organic compounds, however, often results in the production of highly toxic by-products, such as dioxins. Alternative techniques for the destruction of halogenated hydrocarbons include biological treatment and chemical dehalogenation.
Chemical dehalogenation methods convert halogenated organic compounds to less toxic non-halogenated compounds. One such process employs a sodium naphthalene reagent to form sodium chloride and an inert sludge. While the sludge can be safely incinerated, the process is complicated by requiring an air-free reaction vessel that limits its application for on-site treatment of contaminated environmental sources. In another approach, a dechlorination reagent is formed by reacting an alkali metal with polyethylene glycol in the presence of heat and oxygen.
The above-mentioned processes, which involve the oxidative dechlorination of halogenated organic compounds, are generally highly sensitive to water. Such processes require a separation step to remove the halogenated compounds from the aqueous environment before they can be treated. In addition, elevated temperatures are often required to carry out the reaction. Thus, these processes have not been widely accepted for the decontamination of environmental sites (e.g., “Superfund” sites).